Threads, and appologies

[Panzer 4]

My appologies for taking peoples time...

I am NEW to CAD, and am trying an evaluation version of Rhino. It is becomming easiear to use, as I spend more time with it.

My questions are about threads. I have watched the tutorials, and can replicate what is described. I am now running into some other issues.

I am trying to draw some ANSI locknut threads. The pitch is 32, and minor diameter is .436. I have drawn the thread cross section, and when I try to sweep, it does not perform the function, and says that objects are too close together.

So:
Although the tutorials say to sweep a single curve, is it possible to sweep a triangle?

How close can objects be on a sweep?

For CAM, and CNC, doesn't the drawing have to be accurate, and not just a representation of the threads?



Thanks in advance for any advice, or feedback...

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[Panzer 4]

I had a chance to play around a little more tonight, after work.

Conics... It actually turns out pretty sweet.

I am starting to really like this software.

[chmillman]

I am trying to draw some ANSI locknut threads. The pitch is 32, and minor diameter is .436. I have drawn the thread cross section, and when I try to sweep, it does not perform the function, and says that objects are too close together.

What are you trying to sweep your cross section along? In general you get this error message if you have set your sweep up incorrectly, or if there is something wrong with the input curves. I suspect you picked several profiles that are at the same place on the sweep rail.

So:
Although the tutorials say to sweep a single curve, is it possible to sweep a triangle?

Yes - you just need to join the individual lines that make up the triangle into a triangle - use the command Join. A triangle is a single curve. You can have multiple curves in a sweep as cross sections, they just need to be spaced along the curve.

For CAM, and CNC, doesn't the drawing have to be accurate, and not just a representation of the threads?

In most cases you are going to drill/tap or mill/turn the thread with a profile tool, so for CAM having the threads modeled is absolutely useless. For drill holes all you need is a circle or a point... Adding lots of threads to a model when you don't need it is a good way to waste time and to make huge file sizes, so unless you need real lifelike threads for illustration purposes, I recommend not to put them in. However, the exercise in modeling a threaded object once or twice for practice is excellent - it's not that easy, especially if you want to model the runouts correctly at each end. --ch

[ger21]

In most cases you are going to drill/tap or mill/turn the thread with a profile tool, so for CAM having the threads modeled is absolutely useless. For drill holes all you need is a circle or a point... Adding lots of threads to a model when you don't need it is a good way to waste time and to make huge file sizes, so unless you need real lifelike threads for illustration purposes, I recommend not to put them in. However, the exercise in modeling a threaded object once or twice for practice is excellent - it's not that easy, especially if you want to model the runouts correctly at each end.

Agree 100%. I'll model leadscrew threads for the visual, but don't bother with regular screw threads. They can bring your system to it's knees pretty quickly.

[Panzer 4]

Thanks for the replies.

I understand about the cut with a profile tool, and that makes sense.

In learning how to draw with a CAD program, the thread profile has been a good excercise for me. I completed some drawings that kind of amazed me. In the long run, it wasn't that hard. It does take some time.

If anyone has some suggestions for another excersize to test out the capabilities of the software, and as a learning tool, please let me know. I am going to have a tough sell to the wife for an AFE on this.

The inability to draw kept me from taking the plunge on a mill two years ago. I wish that I had sat down to this, back then. There are some parts that I need machined for a prototype that I plan on building over the next few months, and there isn't that much margin for the product. The cost of the prototype is making me a little nervous. It sure would be nice to machine a couple of the parts in my garage during spare time to keep the cost down.